Suspicions fly thick and fast and Irene soon finds herself in the seedy depths of the Parisian underworld. Luckily, she can call on her ex-assistant Kai for assistance. She's on the trail of a notoriously warlike Fae, the Blood Countess. However, the evidence against the Countess is circumstantial. But could the killer really be a member of the Library itself? The fifth title in Genevieve Cogman's witty and wonderful 'The Invisible Library' series